Carbon Bar friction paste

Hey

Didn't know what forum this would fall under but I have some Easton DH Monkey Lite bars that are the CNT(carbon material). In the installation instructions, it mentions putting "Easton Friction Paste" where the bars come in contact with the stem clamp.

How vital is this? If very, where do I find it or what can I substitute for friction paste?

Silicone grease would promote slippage.
What reptilezs said. The gel coat finish on most carbon bars is slippery. Carbon handlebars and seat posts will generally slip without a little help. The paste that most carbon manufacturers sell or provide with carbon bars or seatposts is valve lapping compound or an abrasive derivative to keep the carbon from slipping. The biggest mistake one can make is trying to mitigate slippage by increasing clamp torque...again either stem or seat tube clamp. A better alternative is to use an abrasive paste to increase static friction to allow for lower clamp pressure. Carbon fiber is wonderful stuff but doesn't have the best fracture resistance if over stressed. The very same property that gives carbon its strength makes it prone to breakage if overtorqued. (inelastic)

Obviously you have never tried it, just exactly what do you think they make that fancy carbon paste out of? I have never seen a situation where you need an abrasive to hold a carbon component in place, the grease carrier used in most of these pastes does most of the work by spreading the clamping force under the static load to prevent slippage, the abrasive in the carrier is for those situations where the component sizes are mismatched and you need a filler material to make up the size difference.

If you don't need that filler abrasive to correct a size mismatch then even common spit works fine. Ever wonder why they don't use this crap on carbon fiber aircraft parts? Because you don't need it if the components are sized correctly, they use silicone grease on F18's because it is benign and non-reactive...good enough for me. Its there mainly to prevent crevice corrosion and mitigate fluid migration in between clamping surfaces.

BTW using a petroleum product for epoxy coated carbon fiber can cause issues with swelling on some products;

From Easton:
No grease on carbon posts. Grease contains certain minerals that can attack clear coats, can penetrate the resin matrix and could cause swelling of the composite laminate. Can you say "stuck seat post?" Don't use grease.
John G. Harrington
Vice president, bicycle products
Easton Sports, Inc.

From Campagnolo:
No grease. In some cases it can be dangerous to use grease as the chemical composition can cause a reaction between materials. Besides, it increases the torque required to clamp the post.
Richard Storino
Campagnolo USA

From Deda:
Absolutely no grease on carbon, ever. Also, do not use solvents to get old grease off, or to get old grease out of the seat tube. John Harrington of Easton and I believe that many solvent residues in the seat tube soften the gel coat of the carbon, then bond the gel coat to the inside of the seat tube, freezing the seat post in position for eternity.
Tom Franges
Deda Elementi North America tech support

Obviously you have never tried it, just exactly what do you think they make that fancy carbon paste out of? I have never seen a situation where you need an abrasive to hold a carbon component in place, the grease carrier used in most of these pastes does most of the work by spreading the clamping force under the static load to prevent slippage, the abrasive in the carrier is for those situations where the component sizes are mismatched and you need a filler material to make up the size difference.

If you don't need that filler abrasive to correct a size mismatch then even common spit works fine. Ever wonder why they don't use this crap on carbon fiber aircraft parts? Because you don't need it if the components are sized correctly, they use silicone grease on F18's because it is benign and non-reactive...good enough for me. Its there mainly to prevent crevice corrosion and mitigate fluid migration in between clamping surfaces.

BTW using a petroleum product for epoxy coated carbon fiber can cause issues with swelling on some products;

Chuck...perhaps you know better than I and what makes this forum great. To share opinions. What you write makes some sense. The stuff I have used that comes with different CF seat posts I have used clearly is abrasive. You can feel the grit by rubbing your fingers together. It makes sense to me typical carbon fiber paste...say comprised of silicon grease as the carrier fluid, would have particles suspended in it. These particles would do two things...one act not only as individual stress risers for greater point loading but also keep from pushing all the fluid out due to clamping.,,,the particles acting effectively as stand offs to capture the fluid. This appeals to my sensibilities at least based upon what I know about coef. of static friction.
Perhaps this is an arguable point and maybe there is a best practice and hopefully others will weigh in with their experience.
Cheers.

[QUOTE=4JawChuck]..... the grease carrier used in most of these pastes does most of the work by spreading the clamping force under the static load to prevent slippage,

How does an unconstrained liquid "spread clamping force under static load.." Not sure I understand that concept.

FSA and others make assembly paste for use with CF parts and I understood them all to have some form of friction increasing material (grit, small spheres, etc.) to increase friction. Also on the aerospace side, you typically won't find critical components clamped in place so they may use that silicone for corrosion protection but certainly not for helping hold parts in place through friction.

If you need filler material you can add common household talcum to the grease to increase surface area contact, talc will at least deform under load (I don't recommend this BTW!). The thing that bothers me with those abrasive pastes is how a sharp abrasive forced under load into a carbon matrix affects the carbon fibers. I realize many of those carbon parts have an epoxy coating but is it really a good idea to pierce this protective coating with sharp particles under point loading?

I went looking for an MSDS for any of the common "carbon assembly greases" on the market and couldn't find a single one, you have to wonder how they can sell a product without an MSDS disclosure at all. I know when I asked about this crap at my local bike shop all the guys laughed, they don't even carry it because its a gimmick and said so up front. They recommended roughing up the surface with sandpaper if there is a slipping issue and a little grease to keep it from sticking and protection from interface corrosion especially in a seat tube. Seemed like common sense to me.

BTW silicone grease under static load (clamped) will increase the breakaway friction required to move an object by constrained hydraulic pressure between surface asperities...in other words the grease trapped in the clamp area is squeezing on the bar as much as the clamp is. I could go into how silicone grease has a lower surface tension than petroleum grease as well but then this would become a book on how surface tension affects clamping forces.

Easier to just tell ya to try it and see it work for yourself, I have no reason to lie to you.

Friction paste is great stuff, I use it on all my builds. You might be able to replicate it with a homegrown formula, but you would need to make sure that whatever you put in it will not react with the carbon, even over the long run, so I would be careful about that.

It is paste with pumice like stuff in it. I don't think it has actual pumice or regular grease, for that matter. You only need to apply a tiny bit. It keeps a carbon seatpost from rotating in a frame with much lower seatpost collar bolt torque, for example. And the same idea everywhere. A stem clamping to a carbon bar, components mounting to a carbon bar, carbon steerers, etc. It is amazing. You tighten a fraction of what you feel you need to and things mounted to carbon just won't rotate around the bar.

If you need filler material you can add common household talcum to the grease to increase surface area contact, talc will at least deform under load (I don't recommend this BTW!). The thing that bothers me with those abrasive pastes is how a sharp abrasive forced under load into a carbon matrix affects the carbon fibers. I realize many of those carbon parts have an epoxy coating but is it really a good idea to pierce this protective coating with sharp particles under point loading?

I went looking for an MSDS for any of the common "carbon assembly greases" on the market and couldn't find a single one, you have to wonder how they can sell a product without an MSDS disclosure at all. I know when I asked about this crap at my local bike shop all the guys laughed, they don't even carry it because its a gimmick and said so up front. They recommended roughing up the surface with sandpaper if there is a slipping issue and a little grease to keep it from sticking and protection from interface corrosion especially in a seat tube. Seemed like common sense to me.

BTW silicone grease under static load (clamped) will increase the breakaway friction required to move an object by constrained hydraulic pressure between surface asperities...in other words the grease trapped in the clamp area is squeezing on the bar as much as the clamp is. I could go into how silicone grease has a lower surface tension than petroleum grease as well but then this would become a book on how surface tension affects clamping forces.

Easier to just tell ya to try it and see it work for yourself, I have no reason to lie to you.

You have no reason to lie Chuck and you are a smart guy and likely an engineer like I am so we speak the same language but without a doubt particle laden silicone grease like FSA provides with their carbon product WILL promote better retention than silicone grease without. This is for the reason that you state. The particles which are harder than the epoxy matrix will literally press into the epoxy surface for even greater surface area a.k.a. teeth resulting in a more secure hold. You may not like this dynamic because you suspect it degrades the gel coat in particular but it is no worse and I submit better than roughing up a carbon post to achieve the same end with sand paper. I prefer the silicon grease with grit versus the sand paper route for aesthetic reasons as well.

You do raise a good point however about using silicon grease with no grit and why it would work better than no grease however this may escape some so I will explain a bit. The reason it works even with arguably a lower static coef. of friction is because clamping surface area increases considerably. As Chuck wrote the fluid becomes trapped in the inclusions between handlebar or seat tube and clamp, surface area contact is maximized and therefore retaining force is elevated even with sandwiched medium that is actually lower in friction.

In summary, silicone grease will likely indeed increase retention for the same clamping force versus installing carbon components with nothing. BUT...even though grit in silicone will and does in my experience degrade the gel coat of carbon pieces, make no mistake, grit is added to the substrate carrier fluid to increase friction which it does and why companies like FSA use it. Perhaps plain silicone grease as Chuck suggests maybe good enough for even most but perhaps some might need more who weigh more and ride more aggressively and need a grease with grit.

The purpose of the abrasive carbon paste is to lower the force required to keep the object from slipping.

Carbon paste has a higher coefficient of friction, thus you need less clamping force (in the case of bars) to hold the item in place.

Without carbon paste, I used to have to tighten my stem bolts to around 4-5 Nm to ensure the bars didn't slip. With the paste it only requires 2 - 2.5 Nm to hold the bars without slipping.

This ensures that I come nowhere near cracking the bars from tightening the bolts. You don't need to use it though.

The liquid reduces the friction and allows the two components to slide over each other without binding, thus the materials stresses are uniform loading.

I agree with your statement about uniform loading. That is why NPT and ANPT threads are lubricated before tightening.

Still not sure I can understand why a low friction coefficient material would increase friction between two objects unless there was a hydraulic lock going on on an almost microscopic level. This theory would tend to say that having grease between any two motionless surfaces would increase the breakaway load. Interesting discussion.

I know from empirical testing that the CF assembly paste drastically increases the friction between parts and that regular (non-Silicone) grease allowed slippage at the same and even higher clamping forces.

Still not sure I can understand why a low friction coefficient material would increase friction between two objects unless there was a hydraulic lock going on on an almost microscopic level.
Good discussion

Its because clamping force is pounds force / area. Yes hydrolocking occurs at the atomic level but that isn't the root cause of why a more slippery interface would actually retain better. Its because the amount of surface area contact is greater than the differential in coef. of static (or dynamic) friction with and without it. Surface area rules in other words. Another way to look at it is why fatter tired cars on a lateral skid pad hold at higher G's. Surface area is king for higher adhesion both statically and dynamically.
For nth degree hold however at lowest possible clamp pressure...what we all strive for when clamping carbon fiber....you ideally want both a high coef. of friction and complete surface contact. Keep in mind, with particles in the fluid there is mechanical attachment as well and why it has higher fricition.
Agree...good discussion.

What is comes down to if philosophical is...you want the best clamping for the least clamp pressure AND preserve part integrity. This is where Chuck is right about using generic silicone paste as it will not degrade the gel coat....IF....you can achieve desired clamping. In total, there is a reason why FSA provides what they do with their components. FSA are a high tech company with engineers on staff that have determined that grit in their silicone grease holds better than without it. Yes after clamping with it, it dulls the clearcoat and no longer looks new...the downside.

Didn't know what forum this would fall under but I have some Easton DH Monkey Lite bars that are the CNT(carbon material). In the installation instructions, it mentions putting "Easton Friction Paste" where the bars come in contact with the stem clamp.

How vital is this? If very, where do I find it or what can I substitute for friction paste?

I don't disagree that an abrasive reduces slippage at lower torques, but from experience haven't seen a need to increase the friction coefficient with additive particles unless there is an improper fit issue like using a non-carbon friendly stem with a carbon bar (a big no-no!).

BTW One of my carbon bars has stainless steel mesh imbedded in the carbon matrix which performs the same function as an abrasive, the other bar does not and it has no issues with slippage. I might add my stems (both carbon rated) do not differentiate torque values between carbon or AL bars so the torque is the same for both, I would hesitate to use less torque as the carbon bar would have had to be engineered to be used in the same environment as the AL alternative. In other words I wouldn't be putting less torque on a carbon bar (and using paste to compensate) because I was scared the proper mfg's stated stem torque would damage it.

The issue is moot however as people may find it easier to just spend the $7 dollars and be happy with the results, I however have never seen the need and question the validity of abrasives used in intimate contact with an epoxy fiber product...aircraft have crashed assuming such things. There is a lot of flex at the bar interface and an abrasive inserted into that interface could cause a lot of unseen damage over time, just because they sell it doesn't mean its the best thing to use.

Plain silicone grease is benign and performs 95% of the same function, hence why I recommend you try it before discounting how it works and using an abrasive or "nylon microsphere" alternative.

I don't disagree that an abrasive reduces slippage at lower torques, but from experience haven't seen a need to increase the friction coefficient with additive particles unless there is an improper fit issue like using a non-carbon friendly stem with a carbon bar (a big no-no!).

BTW One of my carbon bars has stainless steel mesh imbedded in the carbon matrix which performs the same function as an abrasive, the other bar does not and it has no issues with slippage. I might add my stems (both carbon rated) do not differentiate torque values between carbon or AL bars so the torque is the same for both, I would hesitate to use less torque as the carbon bar would have had to be engineered to be used in the same environment as the AL alternative. In other words I wouldn't be putting less torque on a carbon bar (and using paste to compensate) because I was scared the proper mfg's stated stem torque would damage it.

The issue is moot however as people may find it easier to just spend the $7 dollars and be happy with the results, I however have never seen the need and question the validity of abrasives used in intimate contact with an epoxy fiber product...aircraft have crashed assuming such things. There is a lot of flex at the bar interface and an abrasive inserted into that interface could cause a lot of unseen damage over time, just because they sell it doesn't mean its the best thing to use.

Plain silicone grease is benign and performs 95% of the same function, hence why I recommend you try it before discounting how it works and using an abrasive or "nylon microsphere" alternative.

My two cents.

I also use the carbon past for my ALUMINUM seatpost on an aluminum frame -- on the clamp and seat rails too. If you adjust your seatpost up and down a lot during rides, it slides easier,works better than any grease, lasts longer, doesn't dry up as quickly, you don't have to mix it with talc, etc. I say it's a no brainer.

I don't disagree that an abrasive reduces slippage at lower torques, but from experience haven't seen a need to increase the friction coefficient with additive particles unless there is an improper fit issue like using a non-carbon friendly stem with a carbon bar (a big no-no!).

Try it without past first. When I installed my Easton bar I simply cleaned all the surfaces with rubbing alcohol and used a file to take down any burrs on the stem. Bolted it down, torqued to spec, and not a single issue with slipping for the almost three years I've had the bar on the bike.

I just got my Easton EC 70 Wide Flat bars for my XTC 29er, and the first thing ya notice is the strange colorations in the sun from the Uni directional carbon fab process. It kind of scared me at first, thought there was some defect, but Zack at Comp Cycle assured me there was no problem, gave me a very good explanation as to why they look the way they do, and noted the LIFETIME warranty from Easton, and their companys history I installed them WITHOUT the paste. Went on a 20 miler, no problems. Granted, I am an old guy, and these are flat bars, and alot less load than a seatpost they didnt budge a micron.
Been getting alot of info from this thread, and is quite interesting to read, what with the battle of the minds going on here.
Saw some bars and stem from a company here:http://www.carbonroadbikebicyclecycl...ars-stem-620mm
No weights, and a $129.00 price for BOTH!
Sounds like the "seems too good to be true" category.